1. Field of the Invention
The present invention relates to an apparatus, a method, and a computer program product for machine translating a sentence that is input in a source language into a sentence in a target language.
2. Description of the Related Art
As the progress of the natural language processing technology goes forward, machine translating apparatuses that convert a sentence input in the first language (source language) and output a sentence in the second language (target language) have been developed. Among those apparatuses, a machine translation system for translating a text in Japanese to other languages such as English and Chinese has been in practical use. Although many translation systems have been suggested for such translating devices, no system has yet been realized that can generate appropriate interpretation for every sentence.
In machine translation, natural language processing technologies including a morphological analysis and a syntactic analysis (dependency analysis) are adopted. As one of the approaches to realizing a high-precision translating machine, it is important to improve the processing precision in each of these technologies. For example, JP-A 2006-53679 (KOKAI) suggests a natural language analyzing device that can offer translation processing with high precision. According to this technology, parse trees included in a parse forest are not individually evaluated, but are entirely subjected to a dependency analysis so that the most plausible interpretation can be selected from among multiple options without falling into a local optimum.
Furthermore, as an approach to realizing high-precision translation, a translating device that translates a sentence of a source language by combining different translation systems has been suggested. For example, JP-A 2001-222529 (KOKAI) suggests a translation technology, with which a sentence input in a source language is segmented into substrings based on the surface patterns of the input sentence, the translation systems are switched around to be operated by selecting the most suitable translation system for each substring, and the translation results are integrated to obtain a translation of the whole sentence.
According to JP-A 2001-222529 (KOKAI), however, the input sentence is segmented in a one-dimensional manner by using its surface patterns such as phrases and clauses as units. For this reason, there is a possibility of restricting types of segmentation patterns and segmenting the sentence in units that are not suitable for the translation. This may hinder improvements in the quality of the translation.